This invention relates to a compact turret type tuner arrangement used in television receivers, and more particularly, to VHF turret television tuners constructed for facilitating the sub-assembly and the main assembly.
Generally, mechanical channel selecting devices for VHF television tuners fall into two groups, namely, the rotary-switching type or the turret type. Turret type tuners include an incrementally rotatably channel selector shaft for selectively connecting certain ones of a plurality of tuned circuit elements to each of a plurality of channel selector positions. For example, such turret tuner arrangements are disclosed in U.S. Pat. Nos. 3,210,700; and 4,128,821, wherein a turret having a plurality of tuning coil units is rotatably mounted on a chassis base. The selected coil unit is connected through terminal contacts to a stator tuning circuit on the chassis base.
The miniaturization of the structure of this kind of mechanical tuners is very difficult in comparison to the rotary switch tuners. However, since television tuners are made in large numbers, it is desirable to provide a low cost turret tuner with a minimum number of parts which may be assembled in an easy and simple manner, in order to be commercially competitive.
In conventional VHF turret tuners the coil units are removably mounted on two or more support discs, and each of the coil units includes an elongate insulator, a coil for an RF input stage, a pair of coils for an intermediate stage between the RF and mixer circuits, and a coil for the local oscillator stage. A screw slidably supported by means of a screw retainer is provided for fine tuning the local oscillator. These coils or windings are wound around the insulator, as disclosed, for example, in U.S. Pat. Nos. 3,227,981; 3,337,949; 3,521,677; 3,594,670; and 3,944,952. Therefore, many parts for turret tuners and complicated assemblies are required.
The conventional detent mechanism, as a means for mounting the rotatable turret on the chassis base, includes a detent wheel fixed on the selector shaft and a spring member mounted on the chassis base, as disclosed in U.S. Pat. Nos. 3,172,062; 3,234,801; 3,407,669; and 3,477,299. It is also known that this kind of spring member may provide resiliency in two different directions. In another type of turret tuner, a sub-assembly for the stationary circuits comprises a printed circuit board, a stator block having a plurality of strips of spring contacts, and necessary electrical elements soldered to each other, as disclosed in U.S. Pat. No. 3,365,621. The use of printed circuit boards sometimes causes stray capacitances harmful for receiving high frequency signals. Further, some devices including lever members, are known as pre-setting, fine tuning devices for VHF turret tuners as disclosed in U.S. Pat. Nos. 3,183,726; 3,316,770 and 4,172,390.
Conventional turret tuners still leave room for improvement, especially as far as minimizing the tuner size and dimension, and simplifying the assembly, as well as lowering the manufacturing costs and improving the tuner performance are concerned.